This simulator models a generic electronic, resettable heat detector: a thermistor bead inside a ventilated shell, connected through fine leads to measurement circuitry that compares element temperature against a fixed-temperature threshold and a filtered rate-of-rise threshold. A controlled warm-air source imposes an air-temperature ramp so you can watch the sensing element lag behind the surrounding air and compare which decision — fixed temperature or rate of rise — trips first.
• Equipment laboratory tab: a real-time cutaway workbench of the ventilated detector shell, thermistor bead, element leads, measurement circuitry, controlled warm-air source and alarm LED, with Home view, Focus selected part, Show full enclosure / cutaway, Exploded view, Auto rotate and Expand camera controls, a numbered clickable component list with callouts, and a labels toggle. • Experiment controls: sliders for starting air temperature (10–45°C), air heating rate (0–30°C/min), element thermal time constant (3–60 s), fixed-temperature threshold (45–90°C) and rate-of-rise threshold (3–15°C/min), an enable/disable checkbox for the rate-of-rise decision, plus Start trial, Stop equipment, Acknowledge and Reset alarm memory actions, a Pause/Advance 0.1 s/Advance 1 s time control with four playback speeds, a live sequence readout, and live metrics (air temperature, sensing-element temperature, filtered element rise rate, fixed threshold, rise-rate threshold, alarm state). • Curves & measurements tab: a primary-measurements chart plotting air temperature, element temperature and the fixed threshold together, a response chart plotting filtered element rise rate against the rise-rate threshold, the underlying model equations, a snapshot-measurements readout and written model-scope notes. • Experiments tab: four guided trials (stable ambient, rapid heating, slow heating with rate-of-rise disabled, and large thermal lag), a "Run model checks" built-in verification suite using independent fresh model instances, and a timestamped event log with a trial-report export. • Learn & assess tab: lesson cards on heating the element, comparing fixed temperature against instantaneous air temperature, evaluating rate of rise with a derivative filter, and identifying this as an electronic resettable detector rather than a fusible non-restoring device, a knowledge-check quiz with reset, and a scope/references panel linking to a mechanical heat-detector manufacturer manual for comparison.
Air temperature in the model rises linearly from the starting temperature at the configured heating rate. The sensing element, however, has thermal mass, so its temperature follows the air temperature with a first-order lag set by the element's time constant — the larger the time constant, the more the element trails behind the surrounding air. The fixed-temperature decision compares element temperature (not instantaneous air temperature) against the configured threshold, which is why a detector with more thermal lag reaches its fixed setpoint later even under the same air-temperature ramp.
The rate-of-rise decision instead watches how fast the element temperature is climbing, using a short derivative filter to avoid triggering on an instantaneous numerical jump. Because rate of rise responds to the slope of heating rather than an absolute temperature, a fast heating rate can trip the rate-of-rise threshold well before the fixed-temperature threshold is reached — exactly what the Rapid heating experiment demonstrates.
The primary-measurements chart lets you compare the imposed air-temperature ramp directly against the lagging element temperature and the fixed threshold line, making the thermal-lag effect visible. The response chart isolates the filtered rise-rate signal against its threshold so you can see exactly when the rate-of-rise decision would fire independent of the fixed-temperature comparison.
The Run model checks button in the Experiments tab exercises the air-temperature ramp equation, the first-order element-lag equation and the filtered-rate calculation against independent fresh model instances, confirming the underlying math behaves consistently. This is a generic electronic thermistor model only: it does not model fire growth, detector spacing rules, a certified response-time index, or the replacement behavior of a fusible, non-restoring fixed-temperature element — the linked mechanical-detector manual is provided purely for comparison, and its mechanism is not simulated here.
The thermistor bead has thermal mass, so it heats up more slowly than the surrounding air. The model represents this with a first-order lag set by an adjustable thermal time constant — a larger time constant means the element trails the air temperature by a larger margin.
Yes. Because rate of rise responds to how fast the element is heating rather than an absolute temperature, a rapid heating rate can trigger the rate-of-rise threshold before the element ever reaches the fixed-temperature setpoint — try the Rapid heating experiment to see this directly.
It models a generic electronic, resettable thermistor-based heat detector with a fixed-temperature threshold and an optional filtered rate-of-rise decision. It does not model a fusible, non-restoring fixed-temperature element, which behaves differently and must be physically replaced after operating.
The Run model checks button in the Experiments tab runs the air-temperature ramp, first-order element-lag and filtered rise-rate equations against independent, freshly created model instances, confirming the teaching model behaves consistently without altering your current trial.